渭河流域干旱特征及干旱指数计算方法初探

Analysis of Drought and Application of Drought Index in the Weihe River Basin

利用游程分析、马尔可夫平稳概率、随机过程等方法分析了渭河流域的干旱特征。结果表明，近44年（1958-2001年）渭河流域降水连续多水（少水）期多持续2～3年，单独多（少）水年出现的概率比连续多水（少水）年的概率大，连少年的概率比连多年的概率大，平均连续少水年数大于平均连续多水年数；枯（丰）水与偏丰（偏枯）之间的转移突变较大，对用水可能带来不利影响；偏枯年出现的概率最大，偏丰年次之，丰水年最小；渭河流域连续少水2～3年不仅发生频率较高，而且干旱强度也较大。同时根据降水和同期气温、天然径流量资料建立了适用于渭河流域的S干旱指数。

The characteristics of drought in the Weihe River basin are analyzed with Markov chain and stochastic process theory. The results show that the continuous wet （dry） periods are usually extended from 2 to 3 years. The probability of a single wet （dry） year is larger than that of continuous wet （dry） years. The probability of continuous dry years is larger than that of continuous wet years. The periods of continuous dry years are longer than that of continuous wet years. The sudden change from a dry year （wet year） to wetter year （drier year） has negative effects for irrigation. The probability of drier year is the greatest, and then wetter year, the probability of wet year is the smallest. The frequencies of the continuous 2- or 3-dry year are high and their intensities are great. In addition, with the partial correlations analysis, the relationship between the precipitation index, the temperature index and the runoff in the Weihe River basin are analyzed. On the basis of these data, the drought index is estimated for the area.